In a stencil duplicator of the prior art, printed sheets of paper are transported by a paper sucking transport belt and are ejected from a paper ejecting device to a paper receiving tray. The paper ejecting device includes a so-called jumping board for adjusting the shape of an ejected sheet, which jumps from the paper ejecting device to the paper receiving tray, to a predetermined shape. With the jumping board, the shape of the ejected sheet is curved to a U-shape (a shape in cross section orthogonal to a transport direction) so as to raise the sheet ends provided in parallel with an axis disposed along a jumping direction.
By forming the shape of the ejected sheet into a U-shape thus, the rigidity of the sheet, that is, the stiffness of the sheet is increased in an axial direction along the transport direction. Thus the leading end of the sheet is prevented from hanging down while the sheet jumps from the paper ejecting device to the paper receiving tray, and the sheet is placed on a predetermined position on the paper receiving tray. Such a technique is described in Japanese Patent Laid-Open No. 56-61266.
Further, Japanese Patent Laid-Open No. 61-217461 describes a configuration for ejecting a sheet of paper while restricting the sheet to a wavy shape along a width direction by a guide member provided along a paper transport direction on a paper transport surface.
Moreover, Japanese Patent Laid-Open No. 2001-58751 describes a configuration in which both edges of a sheet of paper transported on a belt conveyor are guided so as to be raised by an inclined guide member and the sheet is curved into a W-shape substantially at the center of the width of the sheet by protruding members protruding from below to above on a paper transport surface. The urging force of a spring for urging the protruding members in a protruding direction depends upon the stiffness of the sheet.
Further, Japanese Patent Laid-Open No. 6-239000 and Japanese Patent Laid-Open No. 6-239001 each describe a configuration in which movable protruding members are provided so as to move vertically at some points in a paper ejection path for guiding printed sheets of paper, the movable protruding members are vertically driven according to the size of a sheet by a cam driving device, and the heights and positions of the movable members are changed according to the size of the sheet.
In the configuration of the prior art, when a sheet is curved into a W-shape, the amounts of protrusion of the protruding members can be adjusted according to the size and stiffness of the sheet. However, the shape of the ejected sheet which jumps from a paper ejecting device to a paper receiving tray basically remains the same all the time.
However, depending on the kind of paper (size, thickness), the shape of an ejected sheet which jumps from the paper ejecting device to the paper receiving tray may not be adjusted to a desired shape only by curving the sheet into a W-shape.
The present invention has been devised to solve the problem. An object of the present invention is to provide a paper ejecting device for adjusting the shape of an ejected sheet, which jumps from a paper ejecting device to a paper receiving tray, to a desired shape by changing the corrected shape of the sheet according to the kind (size, thickness) of paper and the bias of a surface print rate on the sheet.